Cardiomyopathy

Descriptive text is not available for this image BASICS

DESCRIPTION

  • Cardiomyopathies are myocardial diseases which result in structural and functional heart abnormalities in the absence of coronary artery disease, congenital heart disease, valvular disease, or hypertension which could sufficiently explain the clinical myocardial dysfunction.
  • Results in 5–10% of cases of heart failure
  • Classification of cardiomyopathies
    • Primary (mainly involves the heart)
      • Genetic
        • Hypertrophic cardiomyopathy (HCM)
        • Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D)
        • Left ventricular (LV) noncompaction (LVNC)
        • Glycogen storage (Danon type, PRKAG2)
        • Conduction defects
        • Mitochondrial myopathies
        • Ion channel disorders: long QT syndrome (LQTS), Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT)
      • Mixed (genetic and nongenetic)
        • Dilated cardiomyopathy (DCM)
        • Restrictive (nonhypertrophied and nondilated)
      • Acquired
        • Myocarditis, stress cardiomyopathy, peripartum, tachycardia induced, infants of type 1 diabetic mothers
    • Secondary (multiorgan involvement; see list)
      • Specific: ischemic, valvular, hypertensive, and congenital heart disease

EPIDEMIOLOGY

Incidence

DCM: 5 to 8 new cases per 100,000 population annually

Prevalence

  • DCM: roughly 1:2,500; most common reason for heart transplantation
  • HCM: 1:500 of the adult population; 50% sporadic and rest are familial

ETIOLOGY AND PATHOPHYSIOLOGY

  • HCM: hypertrophied (>15 mm), nondilated left and/or right ventricle which is disproportionate to hemodynamic stress on the heart
  • ARVC/D: involves the right ventricle with progressive loss of myocytes and fatty/fibrofatty tissue replacement; can be associated with myocarditis (adenovirus or enterovirus)
  • LVNC: congenital cardiomyopathies with “spongy” appearance of the LV myocardium
  • LQTS: most common ion channelopathy with prolonged ventricular repolarization and QTc
  • DCM: Ventricular chamber enlargement and systolic dysfunction with normal LV wall thickness result in progressive heart failure and further complications; strong genetic component with infectious and toxic etiologies
  • RCM: normal/decreased ventricular volume with restrictive physiology, biatrial enlargement, and impaired ventricular filling
  • Myocarditis: acute or chronic inflammation of the myocardium produced by toxins, drugs, or infectious causes
  • Peripartum cardiomyopathy (PPCM): a form of DCM with LV systolic dysfunction and heart failure of unknown etiology
  • Stress cardiomyopathies: triggered by profound psychological stress resulting in acute but rapidly reversible LV systolic dysfunction
  • Endocrine: diabetes mellitus, hyperthyroidism, hypothyroidism, hyperparathyroidism, pheochromocytoma, acromegaly
  • Nutritional deficiencies: beriberi, pellagra, scurvy, selenium, carnitine, kwashiorkor
  • Autoimmune/collagen: systemic lupus erythematosus, dermatomyositis, rheumatoid arthritis, scleroderma, polyarteritis nodosa
  • Infectious causes
    • Viral (e.g., HIV, coxsackievirus, adenovirus)
    • Bacterial and mycobacterial (e.g., diphtheria, rheumatic fever)
    • Parasitic (e.g., toxoplasmosis, Trypanosoma cruzi)
  • Infiltrative (1): amyloidosis, Gaucher disease, Hurler disease, Hunter disease, Fabry disease
  • Storage: hemochromatosis, glycogen storage disease (type II, Pompe), Niemann-Pick disease
  • Neuromuscular/neurologic: Duchenne and Emery-Dreifuss muscular dystrophies, Friedreich ataxia, myotonic dystrophy, neurofibromatosis, tuberous sclerosis
  • Toxic: alcohol, drugs, and chemotherapy (anthracyclines, cyclophosphamide, trastuzumab [Herceptin]), radiation, heavy metal, chemical agents
  • Inflammatory (granulomatous): sarcoidosis
  • Idiopathic
  • Endomyocardial: endomyocardial fibrosis, hypereosinophilic syndrome (Loeffler endocarditis)

Genetics

  • Genetic causes are well recognized in HCM; less common in DCM; careful ascertainment of family history, counseling patients with HCM about the potential for genetic transmission of HCM, and options for genetic testing are cornerstones of care (2).
  • Most familial cardiomyopathies are inherited in autosomal dominant pattern (3). Prevalence would be expected to be equal among the sexes, but women are consistently less represented than men in clinical studies across different cardiomyopathies (30–40%) (3). Differences may be explained by various systematic biases in health care attendance and in diagnostic measurements and criteria.
  • Involves mutations in sarcomere contractile proteins

RISK FACTORS

Same as etiology

GENERAL PREVENTION

Some cardiomyopathies which are not inherited can be prevented. Preventive measures include healthy eating habits and lifestyle. Regular moderate intensity exercise, avoidance of polysubstance abuse, management of stress, and maintenance of healthy body weight are recommended. Control of underlying comorbidities like blood pressure and diabetes are also beneficial.

COMMONLY ASSOCIATED CONDITIONS

Cardiomyopathy is commonly associated with coronary artery disease. Infections or noncardiac disease may cause cardiomyopathy, such as viral infections including COVID-19, connective tissue disorders like rheumatoid arthritis and lupus, endocrine disorders like multiple endocrine neoplasia syndromes, systemic infiltrative disorders (e.g., amyloidosis, sarcoidosis), and thyroid related conditions are few conditions associated with cardiomyopathy.

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